President Obama is expected to announce Tuesday that Southern Company will get the nation's first loan guarantees to build the country's first nuclear reactors in three decades.

The guarantees would go toward the construction of two new reactors at Plant Vogtle in Waynesboro, covering project costs if Southern Company defaults, and makes it easier for the company to get loans.

Georgia Power, a subsidiary of the Atlanta-based Southern Company, is a majority owner of Plant Vogtle. The company's share in the project costs and financing charges is about $6 billion. A controversial rate increase -- beginning several years before the reactors begin operation in 2016 and 2017 -- will help pay financing costs.

Opponents, though, say the guarantees are an enormous risk to taxpayers. Huge cost overruns plagued the construction of the first two reactors at Vogtle. Other power companies experienced overruns as well.

A press spokeswoman for Southern Company declined to comment on the guarantees today, saying executives there will wait until after Obama's announcement on Tuesday.

The federal government has allocated $18.5 billion for guarantees for power companies seeking to build nuclear reactors.

Obama is asking that Congress appropriate three times that amount for the next fiscal year.